Download III. Quantum Model of the Atom

III. Quantum Model
of the Atom
(p. 129-134)
Ch. 5 - Electrons in
Atoms
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A. Electrons as Waves
• Louis de Broglie (1924)
– Applied wave-particle theory to e– e- exhibit wave properties
QUANTIZED WAVELENGTHS
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A. Electrons as Waves
QUANTIZED WAVELENGTHS
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A. Electrons as Waves
EVIDENCE: DIFFRACTION PATTERNS
ELECTRONS
VISIBLE LIGHT
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B. Quantum Mechanics
• Heisenberg Uncertainty Principle
– Impossible to know both the velocity and
position of an electron at the same time
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B. Quantum Mechanics
• Schrödinger Wave Equation (1926)
– finite # of solutions  quantized energy levels
– defines probability of finding an e-
Ψ 1s 

1 Z 3/2 σ
π a0
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e
B. Quantum Mechanics
• Orbital (“electron cloud”)
– Region in space where there is 90%
probability of finding an e-
Orbital
Radial Distribution Curve
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C. Quantum Numbers
• Four Quantum Numbers:
– Specify the “address” of each electron in an
atom
UPPER LEVEL
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C. Quantum Numbers
1. Principal Quantum Number ( n )
– Energy level
– Size of the orbital
– n2 = # of orbitals in
the energy level
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C. Quantum Numbers
2. Angular Momentum Quantum # ( l )
– Energy sublevel
– Shape of the orbital
s
p
d
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f
C. Quantum Numbers
• n = # of sublevels per level
• n2 = # of orbitals per level
• Sublevel sets: 1 s,
3 p, 5 d, 7 f
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C. Quantum Numbers
3. Magnetic Quantum Number ( ml )
– Orientation of orbital
– Specifies the exact orbital
within each sublevel
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C. Quantum Numbers
px
py
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pz
C. Quantum Numbers
• Orbitals combine to form a spherical shape.
2s
2px
2py
2pz
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http://www.chem.tamu.edu/rgroup/hughbanks/courses/673/handouts/4f_orbitals.jpg
C. Quantum Numbers
4. Spin Quantum Number ( ms )
– Electron spin  +½ or -½
• Draw them as “up” or “down”
– An orbital can hold 2 electrons that spin in opposite
directions.
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C. Quantum Numbers
• Pauli Exclusion Principle
– No two electrons in an atom can have the
same 4 quantum numbers.
– Each e- has a unique “address”:
1. Principal #
2. Ang. Mom. #
3. Magnetic #
4. Spin #




energy level
sublevel (s,p,d,f)
orbital
Electron (up or down)
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Energy level
Sublevels
Number of Atomic
Orbitals
Total Number of
orbitals
1
s
1
1
2
s
p
1
3
4
3
s
p
d
1
3
5
9
4
s
p
d
f
1
3
5
7
16
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Feeling overwhelmed?
Read
Chapter 5!
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